Question

Student uses lens of focal length 40 and 20 cm find the nature

Answer 1

Student A:40cm

p=1/f

p=1/0.4 (40cm=40/100m)

p=1x10/4

p=+2.5D

converging or convex lens.

Student B:f=-20cm

P=1/f

p=1/-0.2(-20cm=-20/100)

p=1x10/-2

p=-5D

diverging or concave lens.